Process and apparatus for preparing novelty yarns



March 21, 1961 J. G. SMITH 2,975,474 PROCESS AND APPARATUS FOR PREPARINGNOVELTY YARNS Filed June 11, 1958 2 Sheets-Sheet 1 INVENTOR JAMES 6.SMITH ATTORNEY J. G. SMITH March 21, 1961 PROCESS AND APPARATUS FORPREPARING NOVELTY YARNS Filed June 11, 1958 2 Sheets-Sheet 2 INVENTORJAMES 6. SMITH m N mm on N m m mm mm hm ON ATTORNEY Patented Mar. 21,1961 PROCESS AND APPARATUS FOR PREPARING NOVELTY YARNS James G. Smith,Kinston, N.C., assignor to E. I. du Pont de Nemours and Company,Wilmington, Del., a corporation of Delaware Filed June 11, 1958, Ser.No. 741,287

Claims. (Cl. 18-8) This invention relates to a process and apparatus forpreparing novel thick-and-thin yarns from artificial thermoplasticmaterial. More specifically, it relates to an improved method andapparatus for preparing thick-and-thin yarns wherein the deniervariations are arranged in a random fashion.

It is known that a textile yarn having abrupt changes in denier alongits length is capable of producing a fabric possessing novel visual andtactile properties. Several methods have heretofore been proposed forproducing such yarn. For example, thick-and-thin cellulose acetate yarnshave been prepared by passing the yarn around a driven heated rollerhaving its surface indented with longitudinal channels so thatintermittent sections of the yarn are heated, and thereafter applying auniform drawing tension to the yarn. Thick-and-thin yarns of otherartificial thermoplastic materials such as polyethylene terephthalatemay also be prepared in this manner if one starts with undrawn yarn andadjusts the drawing ratio so that the final yarn has alternate drawn andundrawn sections. However, the yarns heretofore prepared in this mannerhave a more or less regularly arranged series of denier variations whichgive a discernible pattern when woven or knitted into fabric. Thisdiscernible pattern is objectionable in many end uses of the finishedmaterial.

Methods have been proposed to eliminate this patterning effect byimparting a random spacing to the yarn denier variations. In general,however, these methods have required complicated apparatus, for example,electronic controls actuated by cosmic rays such as those described byHare in US. Patent 2,622,282.

It is, therefore, an object of this invention to provide an improvedprocess for preparing a novelty yarn of thermoplastic artificialmaterial comprised of alternately disposed and sharply defined large andsmall denier sections wherein the denier variations are spaced in atruly random manner. A further object is to provide a process forpreparing thick-and-thin yarns which do not give a discernible patternwhen woven or knitted into fabric form, A still further object of thisinvention is to provide improved apparatus for preparing novelty yarnshaving random thick-and-thin sections. Otherobjects will be apparentfrom the following description.

The objects of this invention are attained by a process which comprisespassing yarn of an artificial thermoplastic material over a rollerhaving randomly spaced, heated and unheated portions whilesimultaneously traversing the yarn back and forth across the surface ofthe roller at a rate at which the path of the yarn forms an anglegreater than about 60 but less than about 90 with a line parallel to theaxis of the roller. The yarn is withdrawn from the roller at a rate atleast about two times greater than the rate at which it is fed to theroller, thereby drawing the heated portions from about two to twentytimes their original length. Single filaments as well as a plurality offilaments are intended to be included within the term y n r The processof this invention may be, practiced using yam-drawing apparatuscomprised of means for supplying an undrawn yarn at a uniform rate to aroller having randomly spaced abrupt changes in its radial contour sothat the pattern along the contour described by a given helical patharound the roller is significantly different from the pattern describedby any other helical path parallel to but displaced along the axis ofsaid roller from the first path, means for driving said roller, meansfor heating said roller, means for traversing the yarn back and forthacross the surface of said roller, and means for applying a uniformdrawing tension to the yarn leaving said roller.

The invention will be more clearly understood by reference to thefollowing description and accompanying drawings.

In the drawings,

Figure 1 is a perspective illustration of one embodiment of the presentinvention;

Figure 2 is a perspective illustration of another embodiment of theinvention;

Figures 3, 4 and 5 are perspective views of suitable rollers; and

Figure 6 is a perspective view of a suitable traversing mechanism.

With reference to Figure 1, a thermoplastic yarn 1 is passed from asource of supply, not shown, under a guide pin 2, between feed rollers 3and 4, through yarn guide 5 of a reciprocating bar 6, around heated,grooved roller 7, and finally around draw roller 8. The rollers rotateon shafts 9 in the direction shown by the arrows, rollers 3, 4 and 7rotating at the same uniform peripheral speed and roller 8 rotating at ahigher peripheral speed, preferably at least two times the peripheralspeed of rollers, 3, 4 and 7. Ilse yarn is wrapped around draw roller 8a number of times to prevent slippage. After leaving roller 8, the yarnis wound up using a device not shown. Rollers 3, 4 and 8 are unheated,while grooved roller 7 is heated to a suitable temperature. Heating maybe accomplished in any suitable manner, for example, by electrical meansor by stem or other hot fluid which may be circulated through theroller.

The yarn is passed around the heated grooved roller 7, usually makingcontact for at least about 90 of arc, during which time those portionsof the yarn which contact the peripheral areas 10 of the roller becomeheated. The amount of wrap on the roller will, of course, dependsomewhat on the diameter of the particular roller being used. Thedifferential speed between rollers 7 and 8 cause the heated portions ofthe yarn to be drawn as the yarn leaves the grooved roller. The portionsof the yarn which have passed around the roller above the depressedzones or grooves 11 of the roller are unheated and remain substantiallyundrawn, providing sharply defined sections of the yarn which are stillsubstantially the same denier as the original yarn.

Yarn guide 5 is attached to a reciprocating bar 6 which traverses theyarn back and forth, preferably with non-uniform motion, over thesurface of the heated roller. In the preferred method of operation theyarn is traversed rapidly, one complete cycle being completed in aperiod slightly less or greater than the time required for onerevolution of the heated roller. The yarn thus starts each successivetraverse at a different point on the heated roller. Operated in thismanner, a large number of cycles are completed before a pattern isrepeated. For example, if the speed of the traverse is adjusted so thatthe reversal point progresses around the hot roller at the rate of ofthe roller circumference per cycle,

shown, by means of suitable guides to a grooved traverse roller 12,around heated grooved roller 7, and finally around draw roller 8. Therollers rotate on shafts 9 in the direction shown by the arrows, roller8 rotating at a higher peripheral speed than roller 7 in order to givethe desired drawing ratio. Rollers 8 and 12 are unheated, while groovedroller 7 is heated to a suitable temperature. As the yarn passes aroundthe heated grooved roller 7, those portions of the yarn which contactthe peripheral areas 10 of the heated roller become heated. The heatedportions of the yarn are drawn as they leave the grooved roller becauseof the tension exerted by draw roller 8. However, portions of the yarnwhich have passed around the roller above the depressed zones 11 of theroller are unheated and remain substantially undrawn, providing sharplydefined sections of the yarn which are still substantially the samedenier as the original yarn. After leaving roller 8, the yarn is woundup or packaged in any suitable manner.

The grooved traverse roller 12 is operated at such a speed that the yarnfalling in groove 13 is traversed rapidly over the surface of roller 7,completing one traverse cycle in somewhat more or less time than requird.for one revolution of the heated roller. The yarn thus starts eachsuccessive traverse at a different point on the heated roller so that alarge number of cycles are completed before a pattern is repeated.

A convenient method of adjusting the relative speeds of traverse roller12 and heated roller 7 of Figure 2 is to mount two drive wheels on theshafts of the two rollers and bring the peripripheries of the two Wheelsinto frictional contact so that one wheel may drive the other, i.e.,- sothat in effect the traverse roller shaft is driven by the heated rollershaft. With such an arrangement the ratio of the rotational speeds ofthe traverse roller and heated roller is in the inverse of the ratio ofthe diameters of the respective driving wheels. Therefore, the speedratio may be adjusted by appropriate changes in the diameters of thedriving wheels. The number of revolutions the rollers must make beforeexactly repeating a given configuration may be found mathematically bysetting up the ratio of diameters of the two driving wheels in the formof a fraction and dividing both numerator and denominator by theirlargest common factor, or, if one or the other is a fraction,multiplying both numerator and denominator by the smallest numbernecessary to convert both to integers. With the ratio in its revisedform, the larger number (numerator or denominator) gives the number ofrevolutions required of the faster roller, and the smaller number givesthe number of revolutions required of the slower roller, before a givenconfiguration is exactly repeated. For example, if the diameter of thedriving wheel on the heated roller shaft is 6.43 inches, and that of thedriving wheel on the traverse roller shaft is 7.50 inches, their ratiois Since 643 is a prime number, the fraction is now in its simplestform. Therefore, the number of revolutions required of the heated rollerbefore the set of rollers repeats a given configuration is 750.Likewise, the number of revolutions required of the traverse roller is643. In light of the above discussion, it will be obvious that thenumber of revolutions required before a given configuration is repeatedmay be varied within wide limits by picking appropriate driving wheeldiameters with the aid of a table of primes and factors.

The optimum number of traverse cycles per revolution of the heatedroller may be illustrated in terms of the minimum angle attained duringthetraverse cycle be-! tween the yarn path on the surface of the rollerand a line parallel to the axis of the roller. For best results the yarnpath during the traverse cycle is such that the angle between the yarnpath on the surface of the roller and a line parallel to the axis of theroller is greater than about 60 but less than about 90. A fast traversewhich gives an angle appreciably below this range leads to sidewiseslippage of the yarn because of the stretching tension being exerted onthe yarn as it leaves the roller. The number of cycles will also dependon the type of fabric which is to be prepared from the novel yarns.Generally from about 10 to 700 cycles, before a repeat,

' are required to eliminate objectionable patterning. The

lower figure represents the number of cycles required to produce anaverage of one randomly spaced change in denier per inch, and the upperfigure represents the number of cycles required to produce an average ofabout one randomly spaced change in denier for each'twenty inches ofyarn. It may seem surprising that such a large number of cycles arerequired to produce an average of one change in denier per twentyinches. However, experience has proved that accomplishing a truly randomspacing of the changes in denier in such cases is extremely diflicultwith patterning being more readily detected when such large spacings areused.

The traversing mechanism may also be operated with a non-uniform orrandom motion. A suitable random traverse mechanism is shown in Figure 6in which the traverse bar 14, bearing yarn guides 15, is moved back andforth by arm 16 which is pivoted on shaft 17 sup ported by bearing 18.The movement of arm 16 is controlled by the cooperative action of spring19 and cam follower assembly 20 which rides on the outer edge of thenon-uniform multi-lobe cam 21. Cam 21 is driven by shaft 22 whidhis theoutput shaft of speed reducer 23. The input shaft 24 of speed reducer 23is driven by variable speed transmission 25 which in turn is driven byconstant speed motor 26. Pulley 27, mounted on shaft 22 along with cam21, drives pulley 28 on shaft.

29 by means of belt 30. Shaft 29 passes through bracket 39 and driveseccentric 31 which, through arm 32, causes member 33 to oscillate backand forth. This oscillatory motion is carried by shaft 34 and arms 35,36 and 37 to shaft 38. Shaft 38 is the actuating member for varying thespeed of variable speed transmission 25. The non-uniform variation inrotational speed of the nonuniform cam 21 imparts random reciprocatingtranslational motion to guide rod 14, and the yarns 1 passing throughguides 15 mounted on rod 14 are traversed across the surface of slottedroller 40 in truly random fashion.

Figures 3, 4 and 5 illustrate rollers having varying surface contourswhioh may be substituted for roller 7 in Figures 1 and 2. Figure 3 showsa roller having a plurality of indentations consisting of peripheralslots or holes. The slots are spaced in an uneven and random fashion sothat no two helical paths are the same. Figure roller surface andthereby leave unheated sections in the yarn which do not stretch ordraw. The length of the undrawn portion of yarn may be varied by varyingthe height of the vane above the hot surface of the roller. The vanesmay advantageously be inclined on the face of the roller at'an angleequal to the helix angle of the yarn path. Thus, when traversed in onedirection, the yarn may fall on top of a particular vane while whentraversed in the other direction it falls beside it and is not liftedaway from the hot roller surface in the same pattern. Figure 5 shows aroller which has a grooved surface similar to that shown in Figure 1except that the grooves are introduced in a zigzag fashion. The groovesmay also be arranged in other geometrical patterns such as arcs orcircles. It will be apparent that the length of the thick or undrawnportion of the product yarn depends upon the length of unheated yarnwhich is primarily controlled by the width of the groove, slot, or hole,or the height of the raised portion at the heated roller surface. Thedistance between thick sections of the yarn is determined by the lengthof hot roller surface contacted by the yarn between grooves, slots,holes, or raised elements and the draw ratio imposed by the differentialspeed of draw roller and the feed rollers.

The invention will be further described but is not in tended to belimited by the following examples.

EXAMPLE I Apparatus for drawing yarn is arranged as shown in Figure 1,the grooved roller being constructed similarly to roller 7 shown in thefigure. The body of the roller, a right circular cylindricalchrome-plated steel roller four and one half inches in diameter and twoinches wide, is machined to convert the cylindrical surface of theroller into a grooved surface roller. The grooves are spaced on thesurface is indicated in Table l which follows, Where angle A, which ismeasured clockwise, gives the location of the groove around theperiphery of the roller and angle B gives the inclination of the groovefrom a line parallel to the axis of the roller.

Table 1 PLACEMENT OF GROOVES IN HOT ROLL The grooves are 0.060 inch inwidth and 0.090 inch deep: Means for heating the roller consist of threeSO-Watt cartridge heaters mounted in a stationary heater block aboutwhich the roller rotates, the clearance being ,4, inch.

Polyethylene terephthalate polymer, having an intrinsic viscosity of0.63, is melt-spun into a yarn, comprising 27 filaments, having a totalundrawn denier of 135 and a birefringence of 0.0090. In drawing the yarnin the apparatus 1 described above, the feed rollers and the groovedroller are operated to give a yarn speed of 141 yards per minute, andthe yarn is passed around the draw roller at 375 yards per minute. Thespeed of the traverse is arranged so that one traverse cycle iscompleted in slightly less than one revolution of the heated roller, theyarn starting the second traverse at a point about inch from the startof the preceding traverse. The minimum angle during one traverse cyclebetween the yarn path on the surface of the roller and a line parallelto the axis of the roller is about 70. The grooved roller is maintainedat 108 C. The drawn yarn, when examined under magnification, showsabrupt changes in denier with the thick portions having a diameterapproximately 1.7 times that of the intervenin smaller denier segments.

Yarn prepared as described above is woven into a filling-faced satinfabric six inches in width. After finishing, the fabric is found to havethe novel appearance associated with thick-and-thin yarns with nodiscernible evidence of patterning.

Yarn prepared as described above is woven into a 48-inch tafieta fabric.The fabric is secured one-half hour at F., heat-set eight seconds at 325F., and dyed with a dispersed dye for one hour at 205 F. The resultingfabric has the appearance and feel expected of a fabric prepared from athick-and-thin yarn with no discernible evidence of patterning.

Another sample of yarn prepared as above is knit into a two-bar jerseytricot fabric (12 inches per rack). After scouring at the boil forthirty minutes, the fabric assumes an appealing dry, crepe-like handwith no visible pattern formation.

EXAMPLE II Apparatus for drawing yarn is set up as shown in Figure 1except that a roller with raised vanes similar to that shown in Figure 4was substituted for the roller shown in Figure l. The roller, originallya right circular cylinder four and one-half inches in diameter and twoinches wide, is equipped with vanes protruding perpendicularly from thesurface. The vanes are made of wire appropriately bent and inserted intoholes in small purved plates which form the outside surface of the].ller. The roller is heated as described in Example I. i

The height of the vanes is varied with some of the vanes high at one endand low at the other. The higher vanes hold more yarn oif the hot rollersurface than the lower vanes, thereby producing thick-and-thin yarnsections of varying lengths.

The vanes are mounted at an angle equal to the helix angle of thetraversed yarn so that the yarn will pass over the vane when traversedin one direction but will lie beside it when traversed in the oppositedirection. Also, some vanes are spaced in such a fashion thatoccasionally the yarn will pass over two or more vanes without touchingthe hot roller surface between vanes to form very large, thick sections.

Undrawn polyethylene terephthalate yarn prepared as in Example I isdrawn on the apparatus described above at a windup speed of 375 yardsper minute and a draw ratio of 2.9. The speed of the traversingmechanism is adjusted so that one traverse cycle is completed in about0.81 revolution of the heated roller. The actual cycle is such that theheated vaned roller rotates approximately 2000 times before the traversecycle is exactly repeated. The angle between the yarn path on thesurface of the roller and a line parallel to the axis of the roller isabout 70. The vaned roller is maintained at a temperature of 108 C. Thedrawn yarn, when examined under magnification, shows randomly arranged,abrupt changes in denier.

Yarn prepared as described above is woven into a 30- inch wide taffetafabric and found to give the novel appearance associated withthick-and-thin yarns with no discernible' evidence of patterning.

EXAMPLE III A 600-denier, SO-filament cellulose acetate yarn (about 54%combined acetic acid) possessing no twist is stretched using theprocess. described in Example I. The peripheral speed of the hot rolleris .248 inches per minute while the peripheral speed of the take-uproller is 620 inches per minute. The angle between the yarn path on thesurface of the roller and a line parallel to the axis of the roller is75 The width of the grooves in the grooved roller is one-eighth inch andthe roller temperature is maintained at approximately 245 C. Theover-all denier of the stretched yarn is: 240, but abrupt changes indenier are visible along its length. When this yarn is woven into a36-inch taffeta fabric, the characteristic appearance expected of athick-and-thin yarn is obtained, with no discernible evidence ofpatterning.

When yarn prepared by the above process is woven as'filling in a 6-inchwide filling-faced satin fabric, the novel appearance of athick-and-thin yarn is obta ned with no evidence of pattern formation. 7

EXAMPLE IV An apparatus for drawing yarn is set up as described inExample I with the exception that a heated roller four inches widehaving parallel grooves spaced apart in an irregular pattern is used todraw a polyethylene terephthalate yarn. The traverse mechanism isadjusted so that the traverse guide completes a trip across the face ofthe heated roller in one direction in 0.400 revolution of the roller,remains stationary for 0.200 revolution of the roller, makes the returntrip in the opposite direction in 0.460 revolution of the roller, andthen remains stationary for 0.247 revolution of the roller beforebeginning the traverse cycle over again. Thus, the full traverse cycleis completed in 1.307 revolutions of the heated roller, therebyprogressing around the heated roller at the rate of slightly less than/3 of the circumference of the roller per cycle. The heated roller makes1307 revolutions before a given traverse cycle starting point is againencountered.

Theeyarn produced is woven into a 48-inch taffeta fabric which isscoured, heat-set, and dyed as in Example I. The resultant fabric hasthe appearance and handle expected of a fabric prepared from athick-and-thin yarn, with no discernible evidence of patterning. 7

Another sample of yarn prepared as above is woven into a 36-inchfilling-faced satin fabric. The resulting fabric has the appearance andhandle expected of a fabric prepared from thick-and-thin yarn, with nodiscernible evidence of patterning.

In addition to preparing thick-and-thin yarns fromthe materialsdescribed in the foregoing examples, this invention may beadvantageously used to prepare such yarns from a variety of otherfiber-forming materials. Such materials include both natural andsynthetic polymers which are capable of being drawn when heated andplaced under tension. Although yarns which have not been drawn arepreferred, drawn yarns which may be further drawn upon heating may beused. Yarns prepared from polyamides, polysulfonamides, polyesters,polyurethanes, polyureas, polyacrylonitrile, polyhydrocarbons, e.g.,polyethylene, polypropylene, polyvinyl chloride, cellulose esters,cellulose ethers, as well as many others may be drawn by the process ofthis invention.

In practicing this invention, the drawing conditions, e.g., temperatureof the heated roller and tension, will, of course, be determined to alarge extent by the nature of the material being drawn and the amount ofdrawing desired. The speed of drawing will also depend pri-' marily onthese factors. However, as previously indicated, the relative speed oftraverse and the speed of the heated roller should be selected to givemaximum random spacing of the thiek-and-thin sections. Also, thetraversing should be accomplished at a speed at which the angle formedbetween the yarn path on the surface of the roller and a line parallelto the axis of the roller is greater than about 60 but less than about90.

Accordingly, the apparatus of this invention may be modified in variousways. For example, the heated roller may have solid vanes which are heatconducting instead of grooves, or the vanes may be made from a thermalinsulating material. A plurality of yarn guides, heated rollers, anddrawing rollers may be used to draw a number of yarns simultaneously.

The traversing apparatus shown in Figure 6 is also susceptible ofvarious modifications. For example, a suitable arrangement of gears maybe substituted for belt 30 and pulleys 2.7 and 28 in transmitting motionto variable speed transmission 25. Also, a cam and spring arrangementoperating directly from shaft 22. could be used to cause shaft 38 tooscillate, thereby varying the gear ratio in variable speed transmission25. Other modifications will be apparent to those skilled in the art.

The outstanding advantage of the present invention resides in the factthat variable denier yarns having truly randomly spaced thick-and-thinsections are produced. The yarns may be used in many widely differenttypes of woven and knitted fabrics without objectionable patternformation.

It will be apparent that many widely different embodiments of thisinvention may be made without departing from the spirit and scopethereof, and therefore it is not intended to be limited except asindicated in the appended claims.

I claim:

a 1. The process for preparing yarns having randomly spacedthick-and-thin sections which comprises withdrawing a yarn prepared froman artifical thermoplastic material from a supply source at a uniformrate, heating said yarn at randomly spaced intervals by passing saidyarn over a roller having randomly spaced heated portions,simultaneously traversing said yarn back and forth across the surface ofsaid roller at a rate at which the path of said yarn during saidtraversing forms an angle of at least 60 but less than with a lineparallel to the axis of said roller, withdrawing said yarn from saidroller under uniform tension at a uniform rate at least about two timesgreater than the rate at which said yarn is fed to said roller wherebythe sections of said yarn passing in contact with said heated portionsof said roller are drawn from about two to twenty times their originallength.

2. The process of claim 1 wherein said roller makes a plurality ofrevolutions before the original path on the roller is repeated.

3. The process of claim 1 wherein a plurality of yarns are drawnsimultaneously.

4. The process of claim 1 wherein said yarn is caused to traverse thesurface of said roller during less than one revolution of said roller.

5. The process of claim 4 wherein said traversing is intermittent.

6. The process for preparing yarns having randomly spaced thick-and-thinsections which comprises withdrawing an undrawn yarn prepared from anartificial thermoplastic material from a supply source at a uniformrate, heating said yarn at randomly spaced intervals passing said yarnover a roller having randomly spaced heated.

portions, simultaneously traversing said yarn back and forth across thesurface of said roller at a constantly changing rate at which the pathof said yarn during said traversing forms an angle of at least about 60?but less than 90 with a line parallel to the axis of said roller,

withdrawing said yarn from said roller under uniform domly spacedthick-and-thin sections comprising in combination means for supplying aplurality of artificial thermoplastic yarns at a uniform rate to adriven roller, said roller having abrupt changes in its radial contourwhereby the pattern along the contour described by a given helical patharound the roller is significantly different from the pattern describedby any other helical path parallel to but displaced along the axis ofsaid roller, means for heating said roller, a plurality of yarn guidesin advance of said roller mounted on a common member for traversing saidyarns back and forth along the surface of said roller, means operativelyconnected to said member for imparting a non-uniform reciprocatingtranslational motion thereto, and means for applying a uniform drawingtension to the yarn leaving said roller.

9. Apparatus for producing novelty yarn having randomly spacedthick-and-thin sections comprising in combinations means for deliveringan artificial thermoplastic yarn at a uniform rate to driven rollerhaving a plurality of angularly displaced, randomly disposed slotsacross its surface, said slots being so disposed across the surface ofsaid roller that a pattern defined by a given helical path around theroller is significantly different from the pattern defined by any otherhelical path parallel to but displaced along the axis of said roller,means for heating said roller, traversing means in advance of saidroller for imparting a reciprocating translational motion to said yarnwhile passing said yarn over said roller, and means for withdrawing saidyarn from said roller under a uniform tension.

10. In apparatus for producing novelty yarn having randomly spacedthick-and-thin sections, a driven roller having randomly spaced elevatedand depressed sections randomly disposed about its periphery, saidsections being so disposed about the periphery of said roller that apattern defined by a given helical path around the roller issignificantly dilferent from the pattern defined by any other helicalpath parallel to but displaced along the axis of said 5 roller, meansfor forwarding an artificial thermoplastic yarn at a uniform rate tosaid driven roller, traversing means immediately in advance of saidroller for traversing said yarn back and forth across the surface ofsaid roller, means for heating said elevated sections of said 10 rollerand means for withdrawing said yarn from said roller under uniformtension.

References Cited in the file of this patent UNITED STATES PATENTS 151,898,085 Dreyfus et al 'Feb. 21, 1933 2,156,923 Picard May 2, 19392,278,888 Lewis Apr. 7, 1942 2,296,394 Meloon Sept. 22, 1942 2,622,282Hare Dec. 23, 1952 0 2,894,802 Braunlich July 14, 1959 UNITED STATESPATENT OFFICE "CERTIFICATE OF CORRECTION Patent No, 2,975,474 March 21,1961 James G. Smith It is hereby certified that error appears in theabove numbered patent requiring correction and that the said LettersPatent. should read as "corrected below.

Column 2, line 39, for 'stem" read steam column 3, line 31, for"peripripheries" read peripheries column 5, line 21, for "is" read ascolumn 8, line 23, after "least" insert about line 45, after "intervals"insert by column 9, lines 4 and 5, for "combinations" read combinationline 6, after "to" insert me a Signed and sealed this 2nd day of January19626 (SEA L) Attest:

ERNESTW. SWIDER DAVID L. LADD Attesting Officer Commissioner of PatentsUSCOMM-DC-

